Electrophotographic material containing sensitizers

ABSTRACT

An electrophotographic material is provided herein which comprises a conductive support layer and a photoconductive insulating layer, the latter layer comprising a photoconductive polymeric compound such as poly-N-vinylcarbazole, and a sensitizer having the following general formula ##SPC1## 
     Wherein 
     B represents a radical selected from the group consisting of ##SPC2## ##SPC3## 
     Compounds falling under the latter general formula include such compounds as 2-phenyl-4-[(2&#39;-phenyl-4&#39;-benzopyranylidene) benzyl]-benzopyrylium perchlorate and 2,3-phenyl-4-[(2&#39;-phenyl 4&#39;-benzopyranylidene)benzyl]-6-methylbenzopyrylium perchlorate.

This invention relates to novel light-sensitive layers and more particularly to electrophotographic light-sensitive polymer layers.

Various light-sensitive layers are well known in the electrophotographic art for making copies of documents, drawings, transparencies, etc. These layers contain organic photoconductive compounds, such as poly-N-vinylcarbazole, brominated poly-N-vinylcarbazoles, polyacenaphthylene, etc. These layers are non-conductors of electricity before exposure and become electrical conductors upon exposure.

It is necessary for the electrophotographic art that the photoconductive material has a high photoconductivity in the long wavelength region of the visible spectrum. Such a photoconductive material makes it possible for the electrophotograph art to employ inexpensive and convenient light sources such as incandescent lamps in a reduced exposure time and to reproduce colored pictures. The photoconductive materials mentioned above, however, have usually a low photoconductivity and spectrum characteristics sensitive to the short wavelength region of the exposure light and do not satisfy entirely the above requirement.

It is known that an addition of a so-called sensitizer can improve photoconductivity and spectrum characteristics of the above photoconductive compounds. Conventional sensitizers are dyestuff compounds, such as triarylmethane dyes, xanthene dyes, triazine dyes or acridine dyes, but the conventional sensitizers are not entirely satisfactory to improve the photoconductivity and the spectrum characteristics of the available photoconductive compounds.

In addition to the high photoconductivity and spectrum characteristics sensitive to visible light, the electrophotographic art requires a high electric resistance of photoconductive materials in the dark. Conventional sensitizers are apt to increase the dark conductivity whereas they promote the photoconductivity. A high dark conductivity of photoconductive materials is not desirable because it results in a loss of the applied electrostatic charge in the dark.

An object of the invention is to provide electrophotographic materials having a high photoconductivity and spectrum characteristics sensitive to a long wavelength region of the visible spectrum.

Another object of the invention is to provide electrophotographic materials having a high electric resistance in the dark.

These and other objects are accomplished by adding a new sensitizer shown hereinafter to a photoconductive polymeric compound such as poly-N-vinylcarbazole, brominated poly-N-vinylcarbazole or polyacenaphthylene, as a light-sensitive film-forming composition.

The invention is further explained in the following description with reference to the accompanying drawings wherein:

FIG. 1 represents the wedge spectrogram for an electrophotographic material coated with an unsensitized solution of 10 weight percent of brominated poly-N-vinylcarbazole in chlorobenzene.

FIG. 2 represents the wedge spectrogram for an electrophotographic material coated with a solution containing 10 weight percent of brominated poly-N-vinylcarbazole sensitized with 0.04 weight percent of 2-(α-phenyl-p-methoxystyryl)-4-[(2'-phenyl-4'-benzopyranylidene)-methyl]benzopyrylium perchlorate, the brominated poly-N-vinylcarbazole being dissolved in a solvent of four weight parts of chlorobenzene and one weight part of dichloroethane.

FIG. 3 represents the wedge spectrogram for an electrophotographic material coated with a solution containing 10 weight percent of brominated poly-N-vinylcarbazole sensitized with 0.04 weight percent of 2-styryl-3-phenyl-4-[(2'-styryl-4'-benzopyranylidene)methyl]-6-methylbenzopyrylium perchlorate, the brominated poly-N-vinylcarbazole being dissolved in a solvent of four weight parts of chlorobenzene and one weight part of dichloroethane.

FIG. 4 represents the wedge spectrogram for an electrophotographic material coated with a solution containing 10 weight percent of brominated poly-N-vinylcarbazole sensitized with 0.04 weight percent of 2-p-methoxystyryl-4-[2'-α-phenyl-p-methoxystyryl-4'-benzopyranylidene)methyl]benzopyrylium perchlorate, the brominated poly-N-vinylcarbazole being dissolved in a solvent of four weight parts of chlorobenzene and one weight part of dichloroethane.

FIG. 5 represents the wedge spectrogram for an electrophotographic material coated with a solution containing 10 weight percent of brominated poly-N-vinylcarbazole sensitized with 0.04 weight percent of 2-p-methoxystyryl-4-[(2'-phenyl-4'-benzothiopyranylidene)-methyl]benzopyrylium perchlorate, the brominated poly-N-vinylcarbazole being dissolved in a solvent of four weight parts of chlorobenzene and one weight part of dichloroethane.

FIG. 6 represents the wedge spectrogram for an electrophotograph material coated with a solution containing 10 weight percent of brominated poly-N-vinyl carbazole sensitized with 0.04 weight percent of 2-[(2'-phenyl-4'-benzopyranylidene)methyl]3-phenylbenzopyrylium perchlorate, the brominated poly-N-vinylcarbazole being dissolved in a solvent of four parts of chlorobenzene and one weight part of dichloroethane.

FIG. 7 represents the wedge spectrogram for an electrophotographic material coated with a solution containing 10 weight percent of brominated poly-N-vinylcarbazole sensitized with 0.04 weight percent of 2-[(4'-benzothiopyranylidene)methyl]-3-phenylbenzopyrylium perchlorate, the brominated poly-N-vinylcarbazole being dissolved in a solvent of four weight parts of chlorobenzene and one weight part of dichloroethane.

FIG. 8 represents the wedge spectrogram for an electrophotographic material coated with a solution containing 10 weight percent of brominated poly-N-vinylcarbazole sensitized with 0.04 weight percent of 2-[(2'-α-phenyl-p-methoxystyryl-4'-benzopyranylidene)methyl]-3-phenylbenzopyrylium perchlorate, the brominated poly-N-vinylcarbazole being dissolved in a solvent of four weight parts of chlorobenzene and one weight part of dichloroethane.

FIG. 9 represents the wedge spectrogram for an electrophotographic material coated with a solution containing 10 weight percent of brominated poly-N-vinylcarbazole sensitized with 0.04 weight percent of 2-[(2'-phenyl-4'-benzothiopyranylidene)methyl]-3-phenyl-benzopyrylium perchlorate, the brominated poly-N-vinylcarbazole being dissolved in a solvent of four weight parts of chlorobenzene and one weight part of dichloroethane.

The new sensitizer, according to the present invention has the following formula: ##SPC4##

where B represents a radical selected from the group consisting of, ##SPC5## ##SPC6##

R₁ is hydrogen, phenyl or an ethenyl or an ethenyl radical selected from the group consisting of styryl,p-methoxystyryl, 3,4-dimethoxystyryl, α-phenylstyryl, α-phenyl-p-methoxystyryl, β-furyl(α')ethenyl and α-phenyl-β-furyl(α')-ethenyl;

R₂ is hydrogen or phenyl;

R₃ is hydrogen, methyl or phenyl;

R₄ is hydrogen or phenyl;

R₅ is hydrogen, phenyl or an ethenyl radical selected from the group consisting of styryl, p-methoxystyryl, 3,4-dimethoxystyryl, α-phenyl-p-methoxystyryl, β-furyl(α')ethenyl and α-phenyl-β-furyl(α')ethenyl;

R₆ is hydrogen or phenyl;

R₇ is hydrogen, methyl or phenyl;

R₈ is hydrogen or phenyl; .Iadd.

R₉ is hydrogen or p-methoxyphenyl; .Iaddend.

the anion is anionic function selected from the group consisting of perchlorate, fluoroborate, chloroferrate, chlorozincate and nitrate; and

X is oxygen or sulfur atom.

The sensitizers having the formula above mentioned are prepared by the following chemical equations A or B: ##SPC7##

In the case of Equation A, 4-[(4'-benzopyranylidene)-methyl]benzopyrylium derivative (III) is obtained by an addition reaction of 4-methoxybenzopyrylium o-nitrobenzene sulfonate (I) with a benzopyrylium salt (II) in an acetic anhydride solution. The benzopyrylium salt has an active methyl or methylene radical.

In the case of Equation B, 2-[(4'-benzopyranylidene)-methyl]benzopyrylium derivative (V) is obtained by an addition reaction of 4-methoxybenzopyrylium o-nitrobenzene sulfonate (I) with a benzopyrylium salt (IV) in an acetic anhydride solution. The benzopyrylium salt has an active methyl radical.

In both cases, methyl 2,4-dinitrobenzene sulfonate, dimethyl sulfate or methyl iodide can be used instead of methyl o-nitrobenzene sulfonate.

Representative examples of the benzopyranylidenemethylbenzopyrylium salts and benzothiopyranylidene-methylbenzopyrylium salts according to the invention are listed in Table I.

                  Table 1                                                          ______________________________________                                         Compound                                                                       Number             Name of Compound                                            ______________________________________                                          1.    2-phenyl-4-[(2'-phenyl-4'-benzopyranylidene)benzyl]-benzopyrylium              perchlorate                                                              2.    2,3-diphenyl-4-[(2'-phenyl-4'-benzopyranylidene)-benzyl]-6-methylbe            nzopyrylium perchlorate                                                  3.    2,3-diphenyl-4-[(2'-phenyl-4'-benzopyranylidene)-methyl]-6-methylbe            nzopyrylium perchlorate                                                  4.    2,3-diphenyl-4-[(2'-phenyl-4'-benzopyranylidene)-methyl]-6-phenylbe            nzopyrylium perchlorate                                                  5.    2-p-methoxystyryl-4-[(2'-phenyl-4'-benzopyranylidene)-methyl]benzop            yrylium perchlorate                                                      6.    2-β-furyl(α')ethenyl-4-[(2'-phenyl-4'-benzopyranylidene-            methyl]benzopyrylium perchlorate                                         7.    2-(α-phenyl-p-methoxystyryl)-4-[(2'-phenyl-4'-benzopyranylide            ne)methyl]benzopyrylium perchlorate                                      8.    2-styryl-3-phenyl-4-[(2'-phenyl-4'-benzopyranylidene)-methyl]-6-met            hylbenzopyrylium perchlorate                                             9.    2-p-methoxystyryl-3-phenyl-4-[(2'-phenyl-4'-benzopyranylidene)methy            l]-6-methylbenzopyrylium perchlorate                                    10.    9-[(2'-phenyl-4'-benzopyranylidene)methyl]xanthylium perchlorate        11.    2-β-furyl(α')ethenyl-3-phenyl-4-[(2'-phenyl-4'-benzopyra            nylidene)methyl]-6-methylbenzopyrylium perchlorate                      12.    2,3-diphenyl-4-[(2'-styryl-4'-benzopyranylidene)benzyl]-6-methylben            zopyrylium perchlorate                                                  13.    2-phenyl-4-[(2'-styryl-4'-benzopyranylidene)benzyl]benzopyrylium               perchlorate                                                             14.    2,3-diphenyl-4-[(2'-styryl-4'-benzopyranylidene)methyl]-6-methylben            zopyrylium perchlorate                                                  15.    2-(α-phenyl-p-methoxystyryl)-4-[(2'-styryl-4'-benzopyranylide            ne)methyl]benzopyrylium perchlorate                                     16.    2-styryl-3-phenyl-4-[(2'-styryl-4'-benzopyranylidene)methyl]-6-meth            ylbenzopyrylium perchlorate                                             17.    9-[(2'-styryl-4'-benzopyranylidene)methyl]xanthylium perchlorate        18.    2-p-methoxystyryl-3-phenyl-4-[(2'-styryl-4' -benzopyranylidene)meth            yl]-6-methylbenzopyrylium perchlorate                                   19.    2,3-diphenyl-4-[(4'-benzopyranylidene)benzyl]-benzopyrylium                    perchlorate                                                             20.    2-phenyl-4-[(4'-benzopyranylidene)benzyl]benzopyrylium                         perchlorate                                                             21.    2,3-diphenyl-4-[(4'-benzopyranylidene)methyl]-6-methylbenzopyrylium             perchlorate                                                            22.    2-(α-phenyl-p-methoxystyryl)-4-[(4'-benzopyranylidene)methyl]            benzopyrylium perchlorate                                               23.    2-styryl-3-phenyl-4-[(4'-benzopyranylidene)methyl]-6-methylbenzopyr            ylium perchlorate                                                       24.    2-p-methoxystyryl-3-phenyl-4-[(4'-benzopyranylidene)-methyl]-6-meth            ylbenzopyrylium perchlorate                                             25.    9-[(4'-benzopyranylidene)methyl]xanthylium perchlorate                  26.    2-p-methoxystyryl-4-[(4'-benzopyranylidene)methyl]-benzopyrylium               perchlorate                                                             27.    2-p-methoxystyryl-4-[(2'-p-methoxystyryl-4'-benzopyranylidene)methy            l]benzopyrylium perchlorate                                             28.    2-(α-phenyl-p-methoxystyryl)-4-[(2'-p-methoxystyryl-4'-benzop            yranylidene)methyl]benzopyrylium perchlorate                            29.    2-styryl-3-phenyl-4-[(2'-p-methoxystyryl-4'-benzopyranylidene)methy            l]-6-methylbenzopyrylium perchlorate                                    30.    2,3-diphenyl-4-[(2'-p-methoxystyryl-4'-benzopyranylidene)-methyl]-6            -methylbenzopyrylium perchlorate                                        31.    2,3-diphenyl-4-[(2'-p-methoxystyryl-4'-benzopyranylidene)benzyl]-6-            methylbenzopyrylium perchlorate                                         32.    2-phenyl-4-[(2'-p-methoxystyryl-4'-benzopyranylidene)-benzyl]benzop            yrylium perchlorate                                                     33.    9-[(2'-p-methoxystyryl-4'-benzopyranylidene)methyl]-xanthylium                 perchlorate                                                             34.    2-p-methoxystyryl-4-[(4'-benzothiopyranylidene)methyl]-benzopyryliu            m perchlorate                                                           35.    2-(α-phenyl-p-methoxystyryl)-4-[(4'-benzothiopyranylidene)-me            thyl]benzopyrylium perchlorate                                          36.    2-styryl-3-phenyl-4-[(4'-benzothiopyranylidene)methyl]-6-methylbenz            opyrylium perchlorate                                                   37.    2,3-diphenyl-4-[(4'-benzothiopyranylidene)methyl]-6-methylbenzopyry            lium perchlorate                                                        38.    2,3-diphenyl-4-[  (4'-benzothiopyranylidene)benzyl]-6-methylbenzopy            rylium perchlorate                                                      39.    2-phenyl-4-[(4'-benzothiopyranylidene)benzyl]benzopyrylium                     perchlorate                                                             40.    9-[(4'-benzothiopyranylidene)methyl]xanthylium perchlorate.             41.    2-p-methoxystyryl-3-phenyl-4-[(4'-benzothiopyranylidene)-methyl]-6-            methylbenzopyrylium perchlorate                                         42.    2-p-methoxystyryl-4-[(2'-3",4"-dimethoxystyryl-4'-benzopyranylidene            )methyl]benzopyrylium perchlorate                                       43.    2-styryl-3-phenyl-4-[(2'-3",4"-dimethoxystyryl-4'-benzopyranylidene            )methyl]-6-methylbenzopyrylium perchlorate                              44.    9-[(2'-3",4"-dimethoxystyryl-4'-benzopyranylidene)-methyl]xanthyliu            m perchlorate                                                           45.    2-phenyl-4-[(2'-β-furyl(α')ethenyl-4'-benzopyranylidene)            -benzyl]benzopyrylium perchlorate                                       46.    2,3-diphenyl-4-[(2'-β-furyl(α')ethenyl-4'-benzopyranylid            ene)benzyl]-6-methylbenzopyrylium perchlorate                           47.    2,3-diphenyl-4-[(2'-β-furyl(α')ethenyl-4'-benzopyranylid            ene)methyl]-6-methylbenzopyrylium perchlorate                           48.    2-p-methoxystyryl-4-[(2'-β-furyl(α')ethenyl-4'-benzopyra            nylidene)methyl]benzopyrylium perchlorate                               49.    2-(α-phenyl-p-methoxystyryl)-4-[(2'-β-furyl(α')eth            enyl-4'-benzopyranylidene)methyl]benzopyrylium perchlorate              50.    9-[(2'-β-furyl(α')ethenyl-4'-benzopyranylidene)methyl]-x            anthylium perchlorate                                                   51.    2-phenyl-4-[(2'-α-phenylstyryl-4'-benzopyranylidene)-benzyl]b            enzopyrylium perchlorate                                                52.    2-p-methoxystyryl-4-[(2'-α-phenylstyryl-4'-benzopyranylidene)            methyl]benzopyrylium perchlorate                                        53.    2-(α-phenyl-p-methoxystyryl)-4-[(2'-α-phenylstyryl-4'-b            enzopyranylidene)methyl]benzopyrylium perchlorate                       54.    2-phenyl-4-[(2'-α-phenyl-p-methoxystyryl-4'-benzopyranylidene            )benzyl]benzopyrylium perchlorate                                       55.    2,3-diphenyl-4-[(2'-α-phenyl-p-methoxystyryl-4'-benzopyranyli            dene)benzyl] -6-methylbenzopyrylium perchlorate                         56.    2,3-diphenyl-4-[(2'-α-phenyl-p-methoxystyryl-4'-benzopyranyli            dene)methyl]-6-methylbenzopyrylium perchlorate                          57.    2-p-methoxystyryl-4-[(2'-α-phenyl-p-methoxystyryl-4'-benzopyr            anylidene)methyl]benzopyrylium perchlorate                              58.    2-(α-phenyl-p-methoxystyryl)-4-[(2'-α-phenyl-p-methoxys            tyryl-4'-benzopyranylidene)methyl] benzopyrylium perchlorate            59.    9-[(2'-α-phenyl-p-methoxystyryl-4'-benzopyranylidene)-methyl]            xanthylium perchlorate                                                  60.    2-p-methoxystyryl-4-[(2'-α-phenyl-β-furyl(α')ethen            yl-4'-benzopyranylidene)methyl]benzopyrylium perchlorate                61.    9-[(2'-α-phenyl-β-furyl(α')ethenyl-4'-benzopyranyl            idene)methyl]xanthylium perchlorate                                     62.    2-phenyl-4-[(2'-p-methoxystyryl-3'-phenyl-6'-methyl-4'-benzopyranyl            idene)benzyl]benzopyrylium perchlorate                                  63.    2,3-diphenyl-4-[(2'-p-methoxystyryl-3'-phenyl-6'-methyl-4'-benzopyr            anylidene)benzyl]-6-methylbenzopyrylium perchlorate                     64.    2,3-diphenyl-4-[(2'-p-methoxystyryl-3'-phenyl-6'-methyl-4'-benzopyr            anylidene)methyl]-6-methylbenzopyrylium perchlorate                     65.    2-p-methoxystyryl-4-[(2'-p-methoxystyryl-3'-phenyl-6'-methyl-4'-ben            zopyranylidene)methyl]benzopyrylium perchlorate                         66.    2-(α-phenyl-p-methoxystyryl)-4-[(2'-p-methoxystyryl-3'-phenyl            -6'-methyl-4'-benzopyranylidene)methyl]benzopyrylium perchlorate        67.    9-[(2'-p-methoxystyryl-3'-phenyl-6'-methyl-4'-benzopyranylidene)met            hyl]xanthylium perchlorate                                              68.    2-phenyl-4-[(2'-3",4"-dimethoxystyryl-3'-phenyl-6'-methyl-4'-benzop            yranylidene)benzyl]benzopyrylium perchlorate                            69.    2,3-diphenyl-4-[(2'-3",4"-dimethoxystyryl-3'-phenyl-6'-methyl-4'-be            nzopyranylidene)benzyl]-6-methylbenzopyrylium perchlorate               70.    2,3-diphenyl-4-[(2'-3",4"-dimethoxystyryl-3'-phenyl-6'-methyl-4'-be            nzopyranylidene)methyl]  -6-methylbenzopyrylium perchlorate             71.    2-p-methoxystyryl-4-[(2'-3",4"-dimethoxystyryl-3'-phenyl-6'-methyl-            4'-benzopyranylidene)methyl]benzopyrylium perchlorate                   72.    2-(α-phenyl-p-methoxystyryl)-4-[(2'-3",4"-dimethoxystyryl-3'-            phenyl-6'-methyl-4'-benzopyranylidene)methyl]-benzopyrylium                    perchlorate                                                             73.    9-[(2'-3",4"-dimethoxystyryl-3'-phenyl-6'-methyl-4'-benzopyranylide            ne)methyl]xanthylium perchlorate                                        74.    2-phenyl-4-[(2'-β-furyl(α')ethenyl-3'-phenyl-6'-methyl-4            '-benzopyranylidene)benzyl]benzopyrylium perchlorate                    75.    2,3-diphenyl-4-[(2'-β-furyl (α')ethenyl-3'-phenyl-6'-met            hyl-4'-benzopyranylidene)benzyl]-6-methylbenzopyrylium                         perchlorate                                                             76.    2,3-diphenyl-4-[(2'-β-furyl(α')ethenyl-3'-phenyl-6'-meth            yl-4'-benzopyranylidene)methyl]-6-methylbenzopyrylium perchlorate       77.    2-p-methoxystyryl-4-[(2'-β-furyl(α')ethenyl-3'-phenyl-6'            -methyl-4'-benzopyranylidene)methyl]benzopyrylium perchlorate           78.    2-(α-phenyl-p-methoxystyryl)-4-[(2'-β-furyl(α')eth            enyl-3'-phenyl-6'-methyl-4'-benzopyranylidene)methyl]-benzopyrylium             perchlorate                                                            79.    9-[(2'-β-furyl(α')ethenyl-3'-phenyl-6'-methyl-4'-benzopy            ranylidene)methyl]xanthylium perchlorate                                80.    2-phenyl-4-[(2'-phenyl-4'-benzothiopyranylidene)benzyl]-benzopyryli            um perchlorate                                                          81.    2,3-diphenyl-4-[(2'-phenyl-4'-benzothiopyranylidene)-benzyl]-6-meth            ylbenzopyrylium perchlorate                                             82.    2,3-diphenyl-4-[(2'-phenyl-4'-benzothiopyranylidene)-methyl]-6-meth            ylbenzopyrylium perchlorate                                             83.    2-p-methoxystyryl-4-[(2'-phenyl-4'-benzothiopyranylidene)methyl]ben            zopyrylium perchlorate                                                  84.    2-(α-phenyl-p-methoxystyryl)-4-[(2'-phenyl-4'-benzothiopyrany            lidene)methyl]benzopyrylium perchlorate                                 85.    2-p-methoxystyryl-3-phenyl-4-[(2'-phenyl-4'-benzothiopyranylidene)m            ethyl]  -6-methylbenzopyrylium perchlorate                              86.    2-styryl-3-phenyl-4-[(2'-phenyl-4'-benzothiopyranylidene)methyl]-6-            methylbenzopyrylium perchlorate                                         87.    9-[(2'-phenyl-4'-benzothiopyranylidene)methyl]xanthylium                       perchlorate                                                             88.    2-(α-phenyl-p-methoxystyryl)-4-[(2'-phenyl-4'-benzopyranylide            ne)methyl]benzopyrylium fluoborate                                      89.    2-(α-phenyl-p-methoxystyryl)-4-[(2'-phenyl-4'-benzopyranylide            ne)methyl]benzopyrylium chloroferrate                                   90.    2-(α-phenyl-p-methoxystyryl)-4-[(2'-phenyl-4'-benzopyranylide            ne)methyl]benzopyrylium chlorozincate                                   91.    2-[(2'-phenyl-4'-benzopyranylidene)methyl]-benzopyrylium                       perchlorate                                                             92.    2-[(2'-phenyl-4'-benzopyranylidene)methyl]-3-phenylbenzopyrylium               perchlorate                                                             93.    2-[(2'-phenyl-4'-benzopyranylidene)methyl]-3-phenylbenzopyrylium               fluoborate                                                              94.    2-[(2'-phenyl-4'-benzopyranylidene)methyl]-3-phenylbenzopyrylium               chloroferrate                                                           95.    2-[(2'-phenyl-4'-benzopyranylidene)methyl]-3-phenylbenzopyrylium               nitrate                                                                 96.    2-[(2'-styryl-4'-benzopyranylidene)methyl]benzopyrylium                        perchlorate                                                             97.    2-[(2'-styryl-4'-benzopyranylidene)methyl]-3-phenylbenzopyrylium               perchlorate                                                             98.    2-[(4'-benzopyranylidene)methyl]benzopyrylium perchlorate               99.    2-[(4'-benzopyranylidene)methyl]-3-phenylbenzopyrylium                         perchlorate                                                             100.   2-[(2'-p-methoxystyryl-4'-benzopyranylidene)methyl]-benzopyrylium              perchlorate                                                             101.   2-[(2'-p-methoxystyryl-4'-benzopyranylidene)methyl]-3-phenylbenzopy            rylium perchlorate                                                      102.   2-[(4'-benzothiopyranylidene)methyl]benzopyrylium perchlorate           103.   2-[(4'-benzothiopyranylidene)methyl]-3-phenylbenzopyrylium                     perchlorate                                                             104.   2-[(2'-3",4"-dimethoxystyryl-4'-benzopyranylidene)-methyl]benzopyry            lium perchlorate                                                        105.   2-[(2'-3",4"-dimethoxystyryl-4'-benzopyranylidene)-methyl]-3-phenyl            benzopyrylium perchlorate                                               106.   2-[(2'-β-furyl(α')ethenyl-4'-benzopyranylidene)methyl]-b            enzopyrylium perchlorate                                                107.   2-[(2'-β-furyl(α')ethenyl-4'-benzopyranylidene)methyl]-3            -phenylbenzopyrylium perchlorate                                        108.   2-[(2'-α-phenylstyryl-4'-benzopyranylidene)methyl]-benzopyryl            ium perchlorate                                                         109.   2-[(2'-α-phenylstyryl-4'-benzopyranylidene)methyl]-3-phenylbe            nzopyrylium perchlorate                                                 110.   2-[(2'-α-phenyl-p-methoxystyryl-4'-benzopyranylidene)-methyl]            benzopyrylium perchlorate                                               111.   2-[(2'-α-phenyl-p-methoxystyryl-4'-benzopyranylidene)-methyl]            -3-phenylbenzopyrylium perchlorate                                      112.   2-[(2'-α-phenyl-β-furyl(α')ethenyl-4'-benzopyranyl            idene)methyl]-3-phenylbenzopyrylium perchlorate                         113.   2-[(2'-p-methoxystyryl-3',6'-diphenyl-4'-benzopyranylidene)methyl]-            3-phenylbenzopyrylium perchlorate                                       114.   2-[(2'-3",4"-dimethoxystyryl-3',6'-diphenyl-4'-benzopyranylidene)me            thyl]-3-phenylbenzopyrylium perchlorate                                 115.   2-[(2'-p-methoxystyryl-3'-phenyl-6'-methyl-4'-benzopyranylidene)met            hyl]benzopyrylium perchlorate                                           116.   2-[(2'-p-methoxystyryl-3'-phenyl-6'-methyl-4'-benzopyranylidene)met            hyl]-3-phenylbenzopyrylium perchlorate                                  117.   2-[(2'-3",4",-dimethoxystyryl-3'-phenyl-6'-methyl-4'-benzopyranylid            ene)methyl]benzopyrylium perchlorate                                    118.   2-[(2'-3",4"-dimethoxystyryl-3'-phenyl-6'-methyl-4'-benzopyranylide            ne)methyl]-3-phenylbenzopyrylium perchlorate                            119.   2-[(2'-β-furyl(α')ethenyl-3'-phenyl-6'-methyl-4'-benzopy            ranylidene)methyl]benzopyrylium perchlorate                             120.   2-[(2'-β-furyl(α')ethenyl-3'-phenyl-6'-methyl-4'-benzopy            ranylidene)methyl]-3-phenylbenzopyrylium perchlorate                    121.   2-[(2'-phenyl-4'-benzothiopyranylidene)methyl]benzopyrylium                    perchlorate                                                             122.   2-[(2'-phenyl-4'-benzothiopyranylidene)methyl]-3-phenylbenzopyryliu            m perchlorate                                                           123.   2-[(2'-phenyl-4'-benzopyranylidene)methyl]-4-p-methoxyphenylbenzoth            iopyrylium perchlorate                                                  124.   2-[(2'-phenyl-4'-benzopyranylidene)methyl]-3-phenyl-4-p-methoxyphen            ylbenzopyrylium perchlorate                                             125.   2-[(2'-α-phenyl-p-methoxystyryl-4'-benzopyranylidene)-methyl]            -4-p-methoxyphenylbenzothiopyrylium perchlorate                         126.   2-[(2'-α-phenyl-p-methoxystyryl-4'-benzopyranylidene)-methyl]            -3-phenyl-4-p-methoxyphenylbenzothiopyrylium perchlorate                127.   2-[(2'-phenyl-4'-benzothiopyranylidene)methyl]-4-p-methoxyphenylben            zothiopyrylium perchlorate                                              128.   2-[(2'-phenyl-4'-benzothiopyranylidene)methyl]-3-phenyl-4-p-methoxy            phenylbenzothiopyrylium perchlorate                                     ______________________________________                                               Table 2 lists additional information on the absorption maximum in      dichloroethane and melting point of the novel compounds according to the      invention.

                  Table 2                                                          ______________________________________                                         Compound              Absorption Maximum                                       Number   Melting Point                                                                               in dichloroethane (mμ)                                ______________________________________                                          1       135˜139                                                                               415 and 710                                               2       130˜132                                                                               430 and 720                                               3       182˜187                                                                               410 and 630                                               4       164˜170                                                                               635                                                       5       163˜172                                                                               490 and 575                                               6         >300       575 and 660                                               7       162˜169                                                                               500 and 610                                               8       180˜187                                                                               490 and 670                                               9       157˜160                                                                               550 and 670                                              10       103˜105                                                                               610                                                      11       120˜126                                                                               595                                                      12       176˜180                                                                               430 and 700                                              13       122˜126                                                                               420 and 730                                              14       163˜170                                                                               420 and 650                                              15       160˜164                                                                               500 and 600                                              16       166˜169                                                                               495 and 710                                              17       135˜140                                                                               580                                                      18       159˜162                                                                               555                                                      19       179˜181                                                                               420 and 730                                              20       140˜142                                                                               415 and 730                                              21       165˜172                                                                               410 and 700                                              22       174˜178                                                                               500 and 600                                              23       176˜179                                                                               485                                                      24       170˜175                                                                               505                                                      25         >300       630                                                      26         >300       560                                                      27       191˜197                                                                               560                                                      28       201˜203                                                                               500 and 590                                              29       200˜204                                                                               660 and 710                                              30       185˜189                                                                               410 and 650                                              31       178˜183                                                                               430 and 690                                              32       181˜188                                                                               420 and 700                                              33       117˜123                                                                               550 and 650                                              34       185˜189                                                                               590                                                      35       159˜164                                                                               495 and 600                                              36       185˜188                                                                                 610, 650 and 700                                       37       160˜165                                                                               415 and 650                                              38       204˜206                                                                               425 and 700                                              39       166˜169                                                                               415 and 730                                              40         >300       660                                                      41       173˜180                                                                               555                                                      42       175˜181                                                                               540 and 600                                              43       167˜173                                                                               660 and 710                                              44       161˜164                                                                               580 and 720                                              45       145˜150                                                                               415 and 720                                              46       188˜190                                                                               425 and 720                                              47       168˜175                                                                               670                                                      48       171˜176                                                                               490 and 580                                              49       179˜186                                                                               600 and 720                                              50       171˜175                                                                               610 and 660                                              51       151˜155                                                                               480 and 740                                              52       171˜176                                                                               495 and 580                                              53       173˜177                                                                               590 and 700                                              54       140˜147                                                                               550 and 750                                              55       203˜207                                                                               420 and 680                                              56       138˜ 142                                                                              555 and 680                                              57       170˜175                                                                               570                                                      58       154˜157                                                                               585 and 690                                              59       168˜174                                                                               570                                                      60       206˜209                                                                               600                                                      61         >300       650                                                      62       139˜146                                                                               550                                                      63       202˜204                                                                               425 and 700                                              64       173˜177                                                                               530 and 690                                              65       190˜194                                                                               590                                                      66       190˜193                                                                               500 and 600                                              67       192˜195                                                                               620                                                      68       112˜118                                                                               570 and 760                                              69       190˜192                                                                               495                                                      70       154˜159                                                                               650 and 700                                              71       177˜182                                                                               500 and 710                                              72       176˜181                                                                               590                                                      73       195˜199                                                                               495 and 640                                              74       189˜195                                                                               550                                                      75       184˜187                                                                               415 and 720                                              76       192˜196                                                                               640 and 700                                              77         >300       550                                                      78       219˜222                                                                               550                                                      79       226˜230                                                                               630                                                      80       127˜134                                                                               410 and 745                                              81       190˜192                                                                               425 and 730                                              82       156˜159                                                                               665                                                      83       164˜169                                                                               600 and 680                                              84       175˜ 178                                                                              600 and 720                                              85       170˜177                                                                               550 and 700                                              86       157˜166                                                                               650 and 695                                              87       169˜172                                                                               635                                                      88       137˜140                                                                               500 and 610                                              89       167˜172                                                                               500 and 610                                              90       160˜163                                                                               500 and 610                                              91         >300       575                                                      92       128˜134                                                                               575 and 675                                              93       133˜136                                                                               575 and 675                                              94       152˜158                                                                               575 and 675                                              95       133˜138                                                                               575                                                      96       190˜195                                                                               575                                                      97       156˜158                                                                               620 and 690                                              98       225˜229                                                                               565                                                      99       183˜187                                                                               525 and 560                                              100      208˜212                                                                               570                                                      101      170˜176                                                                               630 and 690                                              102      225˜228                                                                               610                                                      103      163˜168                                                                               610 and 690                                              104      178˜184                                                                               510                                                      105      172˜175                                                                               580 and 690                                              106      167˜171                                                                               565 and 620                                              107      190˜194                                                                               560 and 635                                              108      211˜214                                                                               570 and 610                                              109      175˜179                                                                               570 and 610                                              110      198˜201                                                                               570 and 610                                              111      158˜163                                                                               580 and 630                                              112        >300       600 and 645                                              113      185˜188                                                                               570 and 620                                              114      199˜204                                                                               600                                                      115      211˜215                                                                               565 and 600                                              116      177˜181                                                                               570 and 610                                              117      205˜207                                                                               570                                                      118      190˜194                                                                               590                                                      119      237˜241                                                                               560                                                      120        >300       590                                                      121      207˜210                                                                               565 and 605                                              122      155˜158                                                                               615 and 675                                              123      143˜145                                                                               615                                                      124      126˜131                                                                               619                                                      125      144˜148                                                                               559 and 657                                              126      140˜142                                                                               589 and 663                                              127      149˜153                                                                               656                                                      128      141˜145                                                                               660                                                      ______________________________________                                    

The following description will explain a practical method for making benzopyranylidene-methylbenzopyrylium salts or benzothiopyranylidene-methylbenzopyrylium salts with reference to exemplary compounds. The details of the preparation of other compounds will be apparent to the skilled in the art from the preceding disclosure and the following illustrative examples of preparation methods of various compounds according to the invention:

(a) 2-phenyl-4-[(2'-phenyl-4'-benzopyranylidene)-benzyl]benzopyrylium perchlorate (compund number 1) ##SPC8##

5.5 Grams of 2-phenyl-4-methoxybenzopyrylium o-nitrobenzene sulfonate, which is obtained from flavone and methyl o-nitrobenzenesulfonate, and 5 grams of 2-phenyl-4-benzylbenzopyrylium perchlorate are dissolved in 150 milliliters of acetic anhydride to a solution. The solution is then refluxed for 15 minutes and poured into 900 milliliters of 10 weight percent perchloric acid. The solution is filtered to obtain a precipitate. The precipitate is dried and dissolved again in dichloroethan to a solution. For purification the solution is poured into ether. Precipitated crystals are filtered off, washed with ether and dried to obtain 4 grams (theoretical yield 53%) of green crystals having a melting point of 135° to 139° C.

(b) 2-(α-phenyl-p-methoxystyryl)-4-[(2'-phenyl-4'-benzopyranylidene)methyl]benzopyrylium perchlorate (compound number 7) ##SPC9##

5.5 grams of 2-(α-phenyl-p-methoxystyryl)-4-methylbenzopyrylium perchlorate and 5.5 grams of 2-phenyl-4-methoxybenzopyrylium o-nitrobenzene sulfonate are dissolved in 150 milliliters of acetic anhydride to a solution. The solution is then refluxed for 15 minutes and poured into 900 milliliters of 10 weight percent perchloric acid. The solution is filtered to obtain a precipitate. The precipitate is reprecipitated with dichloroethane ether. Precipitated crystals are filtered off, washed with ether and dried to obtain 5.5 grams (theoretical yield 69%) of blue crystals having a melting point of 162° to 169°C. In the procedure above mentioned the solution ios poured into an ether solution of BF₃.O(C₂ H₅)₂ instead of 10 weight percent perchloric acid. In this case 2-(α-phenyl-p-methoxystyryl)-4-[(2'-phenyl-4'-benzopyranylidene)methyl]benzopyrylium fluoroborate (compound number 88) is obtained. In the procedure when the solution is poured into a 10 weight percent zinc chloride aqueous solution, 2-(α-phenyl-p-methoxystyryl)-4-[(2'-phenyl-4'-benzopyranylidene)-methyl]benzopyrylium chlorozincate (compound number 90) is obtained.

(c) 2-p-methoxystyryl-3-phenyl-4-[(2'-styryl-4'-benzopyranylidene)methyl]-6-methylbenzopyrylium perchlorate (compound number 18) ##SPC10##

2-styryl-4-methoxybenzopyrylium o-nitrobenzenesulfon (melting point, 155° to 157° C) is obtained by a reaction of 2-styrylchromone and methyl o-nitrobenzenesulfonate in dry benzene at 50° C for 24 hours. According to the same reaction as shown in procedure (a), 2-styryl-4-methoxybenzopyrylium o-nitrobenzenesulfonate reacts with 2-p-methoxystyryl-3-phenyl-4,6-dimethylbenzopyrylium perchlorate to obtain 2-p-methoxystyryl-3-phenyl-4-[(2'-styryl-4'-benzopyranylidene)methyl]-6-methylbenzopyrylium perchlorate crystals which have a color of reddish violet in dichloroethane and have a melting point of 159° to 162° C. The product is obtained in 73% yield.

(d) 2-(α-phenyl-p-methoxystyryl)-4-[(4'-benzopyranylidene)-methyl]benzopyrylium perchlorate (compound number 22) ##SPC11##

4-methoxybenzopyrylium o-nitrobenzenesulfonate reacts with 2-(α-phenyl-p-methoxystyryl)-4-methyl]benzopyrylium perchlorate to 2-(α-phenyl-p-methoxystyryl)-4-[(4'-benzopyranylidene)methyl]-benzopyrylium perchlorate in the same procedure as the procedure (a). The crystals have a color of violet in dichloroethane and a melting point of 174° to 178°C. The product is obtained in 95% yield.

(e) 2-p-methoxystyryl-4-[(2'-3",4"-dimethoxystyryl-4'-benzopyranylidene)methyl]benzopyrylium perchlorate (compound number 42) ##SPC12##

2-(3',4'-Dimethoxystyryl)-4-methoxybenzopyrylium o-nitrobenzenesulfonate (melting point 211° to 213°C) is obtained from a reaction of 2-(3',4'-dimethoxystyryl)chromone and methyl o-nitrobenzene sulfonate. 6.5 Grams of 2-(3',4'-dimethoxystyryl)-4-methoxybenzopyrylium o-nitrobenzenesulfonate and 4,5 grams of 2-p-methoxystyryl-4-methylbenzopyrylium perchlorate are dissolved in 150 milliliters of acetic anhydride to a solution. The solution is heated at 100°C for 100 minutes. After cooling the solution is poured into 900 milliliters of 10 weight percent perchloric acid. Precipitates are filtered off and dried. For purification, reprecipitation is made using dichlorethane and ether. 3.2 Grams of product is obtained in 41% yield. The product has a color of drak violet in dichloroethane and a melting point of 175° to 181°C.

(f) 2-(α-phenyl-p-methoxystyryl)-4-(2'-p-methoxystyryl-3'-phenyl-6'-methyl-4'-benzopyranylidene)methyl]-benzopyrylium perchlorate (compound number 66) ##SPC13##

2-p-Methoxystyryl-3-phenyl-4-methoxy-6-methylbenzopyrylium o-nitrobenzenesulfonate (melting point 141° to 144°C) is obtained from 2-p-methoxystyryl-3-phenyl-6-methylchromone and methyl o-nitrobenzenesulfonate. 2-p-methoxystyryl-3-phenyl-4-methoxy-6-methylbenzopyrylium o-nitrobenzenesulfonate reacts with 2-(α-phenyl-p-methoxystyryl)-4-methylbenzopyrylium perchlorate in the same procedure as the procedure (e). The product has a color of violet in dichloroethane and a melting point of 190° to 193° C.

(g) 2-p-methoxystyryl-3-phenyl-4-[(2'-phenyl-4'-benzothiopyranylidene)methyl]-6-methyl]benzopyrylium perchlorate (compound number 85) ##SPC14##

2-phenyl-4-methoxybenzothiopyrylium o-nitrobenzenesulfonate is obtained from thioflavone and methyl o-nitrobenzenesulfonate. As the same procedure as procedure (e), the product is obtained in 62% yield. The product has a color of reddish violet in dichloroethane and a melting point of 170° to 177° C.

(h) 2-[(2'-phenyl-4'-benzopyranylidene)methyl]-3-phenylbenzopyrylium perchlorate (compound number 92) ##SPC15##

5.5 grams of 2-phenyl-4-methoxybenzopyrylium o-nitrobenzenesulfonate, which is obtained from flavone and methyl o-nitrobenzenesulfonate, and 4 grams of 2-methyl-3-phenylbenzopyrylium perchlorate are dissolved in 150 milliliters of acetic anhydride to a solution. The solution is heated at 100° C for 15 minutes. After cooling the solution is poured into 900 milliliters of 10 weight percent perchloric acid. Precipitated product is filtered off and dried. For purification, reprecipitation is made using dichloroethane and ether. The product has a color of blue in dichloroethane and a melting point of 128° to 134° C. The product yields 3 grams (theoretical yield 46%). Compound number 93 (fluoborate), compound number 94 (chloroferrate) or compound number 95 (nitrate) is obtained using either solution of borontrifluoride etherate, aqueous solution of ferric chloride or diluted nitric acid respectively instead of 10 weight percent perchloric acid.

(i) 2[(2'-4-phenyl-p-methoxystyryl-4'-benzopyranylidene)methyl]-3-phenylbenzopyrylium perchlorate (compound number 11) ##SPC16##

2-(α-Phenyl-p-methoxystyryl)-4-methoxybenzopyrylium o-nitrobenzenesulfonate, which is obtained from 2-(α-phenyl-p-methoxystyryl)chromone and methyl o-nitrobenzenesulfonate, reacts with 2-methyl-3-phenylbenzopyrylium perchlorate in the same procedure as procedure (h). The reaction product yields in 43%. The product has a color of violet in dichloroethane and a melting point of 158° to 163°C.

It has been discovered according to the invention the compounds listed in Table 1 are sensitizing agents which can improve the photoconductivity and the spectrum characteristics of photoconductive polymeric compounds such as poly-N-vinylcarbazole, brominated poly-N-vinylcarbazoles, polyacenaphthylene, etc. These polymers, except brominated poly-N-vinylcarbazoles, are prepared in a per se well known method. The brominated poly-N-vinylcarbazole can be prepared by the following method: To the solution of 20 grams of poly-N-vinylcarbazole in 450 milliliters of chlorobenzene, there are added 18.44 grams of N-bromosuccinimide and 0.173 grams of benzoyl peroxide. The mixture is heated at 80°C for 2 hours while being stirred thoroughly and is poured into methanol to obtain a white polymer. The polymer is dissolved in chlorobenzene and again poured into methanol for purification. The pure polymer thus obtained as a precipitate exhibits upon elementary analysis a halogen content of 29.87 weight percent which approximates the value calculated, i.e. 29.44 weight percent of the monobromosubstituted product from poly-N-vinylcarbazole. This indicates that the polymer obtained is a monobromosubstituted product. The degree of bromination varies from 50 mole percent to 200 mole percent according to reaction conditions.

The novel sensitizer comprising at least one compound from the group listed in Table 1 is dissolved in a suitable solvent, such as dichloroethane, methylene chloride, chloroform, or a combination thereof, and is added to the solution of the photoconductive polymer described above. The preferable amount of the sensitizer added is from 0.01 to 3.0 weight parts in connection with 100 weight parts of the photoconductive polymer. Advantageously, the amount thereof is from 0.1 to 2.0 weight parts in connection with 100 weight parts of the photoconductive polymer.

For the preparation of the photoconductive insulating layer, a said solution of the photoconductive polymer and the sensitizer in a suitable solvent is applied to the electroconductive support in per se usual manner, for example, by spraying, by means of bladed coating, by means of whirler coating, etc., and then dried so as to produce a homogeneous photoconductive insulating layer on the electroconductive support. Operable solvents are benzene, toluene, chlorobenzene, dioxane, methylene chloride, dichloroethane and combinations thereof. Said solution may be incorporated with suitable plasticizers and/or organic colloids for improving the flexibility and strength of the photoconductive polymer. Operable plasticizers are as follows: chlorinated diphenyl, dimethyl phthalate, diethyl phthalate and octyl phthalate. Operable organic colloids are as follows: natural and synthetic resins, e.g. phenol resin, phenol resin modified with resin, polyvinyl acetal, polyvinyl butyral, polyvinyl cinnamate, polycarbonate resin. Operable materials for electroconductive supports may be made of any materials which satisfy the requirement of the electrophotographic art, e.g. metal plate or glass plate having NESA coating, plate or foil made of electrically conductive resin or coated with evaporated thin metal layer. If paper is to be used as a support for the photoconductive layer, pretreatment of the paper against penetration of the coating solution in advisable. The transparent support can produce a transparent electrophotographic plate, foil or film. After an electrostatic charge has been applied, i.e. after the layer has been charged positively or negatively by means of a corona discharge, the layer becomes light sensitive.

The reproduction of images by the electrophotographic method is carried out as follows: when the photoconductive layer has been charged by means of a corona discharge apparatus, the support with the sensitized layer is exposed to light under a master and is then dusted over in a per se known manner with a resin powder colored with carbon black. The image that now becomes visible can easily be wiped off. It can also be fixed by heating at about 120°C. From positive masters, positive images characterized by good contrast the producted.

This invention is still further illustrated with reference to the following illustrative examples.

EXAMPLE 1

1 Gram of polyacenaphthylene and 0.6 gram of, as a plasticiser, chlorinated diphenyl (commercially available as "Kanechlor"), are dissolved in 8 milliliters of chlorobenzene. To the solution are added 0.5 milliliters of dichloroethane containing 0.006 gram of a sensitizer corresponding to compound number listed in Table 1. The solution is applied to an aluminum plate by means of whirler coating and is dried to form a layer of 7μ in thickness. After said aluminum plate provided with the layer is charged negatively by means of corona discharge with a charging device maintained at approximately 6000 volts in the dark, it is placed under a positive master and is exposed to a 100W tungsten lamp at an illumination of 50 luxes, and the said plate is powdered over with a developer in a per se known manner. This developer consists of toner and carrier. The toner consists of low melting point polystyrene, colophony and carbon black. The toner is mixed with a carrier substance such that the toner becomes triboelectrically charged with a charge opposite to that produced on the plate. A positive image is produced and is fixed by slight heating. In Table 2, there are shown the optimum amounts of exposure in lux-second units.

                  Table 2                                                          ______________________________________                                         Compound Number                                                                               Optimum Exposure (lux.sec)                                      ______________________________________                                         none           200000                                                           5             320                                                              7             300                                                              9             75                                                              15             180                                                             16             110                                                             18             65                                                              33             135                                                             35             480                                                             41             105                                                             42             320                                                             51             380                                                             52             140                                                             53             290                                                             54             140                                                             58             130                                                             60             175                                                             65             140                                                             71             180                                                             92             70                                                              97             150                                                             103            100                                                             105            120                                                             109            130                                                             110            180                                                             111            70                                                              112            170                                                             113            120                                                             116            115                                                             ______________________________________                                    

EXAMPLE 2

1 Gram of poly-N-vinylcarbazole, chlorinated diphenyl (commercially available as "Kanechlor") and 0.006 gram of a sensitizer, coresponding to compound number listed in Table 1, in 10 milliliters of dichloroethane to a solution. The solution is applied to an aluminum plate by means of blade coating and is dried to form a layer of 10μ in thickness. An electrophotographic image in the same way as that described in Example 1. In Table 3, there are shown the optimum amounts of exposure in lux-second units to produced exactly the original images.

                  Table 3                                                          ______________________________________                                         Compound Number                                                                               Optimum Exposure (lux.sec)                                      ______________________________________                                         none           20000                                                            1             50                                                               2             220                                                              3             60                                                               4             70                                                               5             22                                                               6             44                                                               7             26                                                               8             62                                                               9             44                                                              10             48                                                              11             160                                                             12             220                                                             13             90                                                              14             75                                                              15             28                                                              16             36                                                              17             115                                                             18             22                                                              23             180                                                             26             110                                                             27             44                                                              28             36                                                              29             40                                                              30             60                                                              32             120                                                             33             36                                                              34             50                                                              35             30                                                              36             46                                                              37             90                                                              41             52                                                              42             44                                                              43             48                                                              45             75                                                              47             58                                                              48             34                                                              49             35                                                              50             70                                                              51             30                                                              53             26                                                              54             28                                                              56             28                                                              57             20                                                              58             24                                                              59             36                                                              60             44                                                              61             44                                                              62             100                                                             64             54                                                              65             44                                                              66             22                                                              67             74                                                              70             56                                                              71             20                                                              72             22                                                              76             60                                                              78             38                                                              80             46                                                              82             50                                                              83             24                                                              84             19                                                              85             17                                                              86             54                                                              87             42                                                              88             25                                                              89             28                                                              90             30                                                              91             140                                                             92             18                                                              93             20                                                              34             23                                                              95             40                                                              96             66                                                              29             24                                                              98             230                                                             99             460                                                             100            50                                                              101            36                                                              102            115                                                             103            36                                                              104            68                                                              105            19                                                              106            120                                                             107            58                                                              108            76                                                              109            46                                                              110            36                                                              111            20                                                              112            42                                                              113            48                                                              114            54                                                              115            54                                                              116            52                                                              117            64                                                              118            50                                                              119            135                                                             120            90                                                              121            30                                                              122            28                                                              ______________________________________                                    

It is clear from Table 3 that the novel sensitizers improve the photoconductivity of poly-N-vinylcarbazole.

EXAMPLE 3

1 Gram of brominated poly-N-vinylcarbazole (monobromo-substituted product), 0.5 gram of polycarbonate resin (commercially available as "Panlite-C"), 0.3 gram of chlorinated diphenyl (commercially available as "Kanechlor") and 0.002 gram of sensitizer listed in Table 1 are dissolved in a mixed-solvent of 8 milliliters of chlorobenzene and 2 milliliters of dichloroethane. This solution is applied to an aluminum plate by means of a blade coating and dried to form a layer of 14μ in thickness. On this support, electrophotographic images are produced in the same way as that described in Example 1. Table 4 shows the optimum amounts of exposure in lux-second units to reproduce exactly the original images.

                  Table 4                                                          ______________________________________                                         Compound Number                                                                               Optimum Exposure (lux.sec)                                      ______________________________________                                         none           80000                                                            1             75                                                               2             280                                                              3             67                                                               4             44                                                               5             20                                                               6             26                                                               7             18                                                               8             30                                                               9             22                                                              10             40                                                              11             120                                                             12             400                                                             13             110                                                             14             75                                                              15             25                                                              16             28                                                              17             135                                                             18             23                                                              19             410                                                             20             340                                                             21             180                                                             22             40                                                              23             130                                                             24             60                                                              25             300                                                             26             100                                                             27             52                                                              28             52                                                              29             48                                                              30             110                                                             31             320                                                             32             270                                                             33             27                                                              34             30                                                              35             26                                                              37             52                                                              38             440                                                             39             110                                                             40             125                                                             41             22                                                              42             28                                                              43             32                                                              44             75                                                              45             105                                                             46             170                                                             47             42                                                              48             32                                                              49             35                                                              50             50                                                              51             48                                                              52             20                                                              53             19                                                              54             42                                                              55             230                                                             56             26                                                              57             22                                                              58             24                                                              59             23                                                              60             26                                                              61             36                                                              62             130                                                             63             190                                                             64             44                                                              65             26                                                              66             20                                                              67             46                                                              68             75                                                              69             115                                                             70             42                                                              71             18                                                              72             20                                                              73             48                                                              74             110                                                             75             115                                                             76             70                                                              77             44                                                              78             35                                                              79             75                                                              80             50                                                              81             145                                                             82             35                                                              83             20                                                              84             19                                                              85             17                                                              86             34                                                              87             34                                                              88             20                                                              89             20                                                              90             25                                                              91             100                                                             92             15                                                              93             17                                                              94             16                                                              95             40                                                              96             52                                                              97             26                                                              98             180                                                             99             140                                                             100            46                                                              101            36                                                              102            58                                                              103            20                                                              104            34                                                              105            21                                                              106            80                                                              107            44                                                              108            40                                                              109            23                                                              110            26                                                              111            17                                                              112            26                                                              113            28                                                              114            40                                                              115            44                                                              116            28                                                              117            44                                                              118            36                                                              119            105                                                             120            52                                                              121            26                                                              122            21                                                              123            15                                                              124            25                                                              125            17                                                              126            14                                                              127            11                                                              128            13                                                              ______________________________________                                    

It is clear from Table 4 and FIGS. 1 to 9 that the novel sensitizers improve the photoconductivity and the spectrum characteristics of brominated poly-N-vinylcarbazole.

The invention has been described in detail with particular reference to preferred embodiments thereof, but it will be understood that variations and modifications can be effected within the spirit and scope of the invention as described hereinabove and as defined in the appended claims. 

What we claim is:
 1. An electrophotographic material comprising a conductive support layer and photoconductive insulating layer, the latter comprising a combination of a photoconductive polymeric compound and a sensitizing amount of a sensitizer having the following formula: ##SPC17##wherein B represents a radical selected from the group consisting of ##SPC18## ##SPC19## R₁ is hydrogen, phenyl or an ethenyl radical selected from the group consisting of styryl, p-methoxystyryl, 3,4-dimethoxy-styryl, α-phenylstyryl, α-phenyl-p-methoxystyryl, β-furyl(α')ethenyl and α-phenyl-β-furyl(α') ethenyl; R₂ is hydrogen or phenyl; R₃ is hydrogen, methyl or phenyl; R₄ is hydrogen or phenyl; R₅ is hydrogen, phenyl or an ethenyl radical selected from the group consisting of styryl, p-methoxystyryl, 3,4-dimethoxy-styryl, α-phenyl-p-methoxystyryl, β-furyl(α')ethenyl and α-phenyl-β-furyl(α')ethenyl; R₆ is hydrogen or phenyl; R₇ is hydrogen or phenyl; .Iadd. R₈ is hydrogen or phenyl; R₉ is hydrogen or p-methoxyphenyl; .Iaddend. the anion is an anionic function selected from the group consisting of perchlorate, fluoroborate, chloroferrate, chlorozincate and nitrate; and X is oxygen or a sulfur atom; said photoconductive polymeric compound comprising at least one compound selected from the group consisting of poly-N-vinylcarbazole, brominated
 2. An electrophotographic material according to claim 1, wherein said sensitizer comprises at least one compound selected from the group consisting of 2-(α-phenyl-p-methoxystyryl)-4-[(2'-phenyl-4'-benzopyranylidene)methyl]benzopyrylium perchlorate, 2-p-methoxystyryl-4-[(2'-3",4"-dimethoxystyryl-3'-phenyl-6'-methyl-4'-benzopyranylidene)methyl]benzopyrylium perchlorate, 2-[(2'-phenyl-4'-benzopyranylidene) methyl]-3-phenyl benzopyrylium fluoroborate, 2-[(2'-phenyl-4'-benzopyranylidene)methyl]-4-p-methoxyphenyl benzothiopyrylium perchlorate, and 2-[(2'-phenyl-4'-benzothiopyryanylidene)methyl]-4-p-methoxyphenyl
 3. An electrophotographic material according to claim 1, wherein said combination comprises 100 weight parts of photoconductive polymeric compound and 0.01 to 3.0 weight parts of sensitizer. 